The studies proposed in this project deal with the specific affinity of haptoglobin (Hp) for hemoglobin (Hb) and the role of this affinity in the evolution of Hp structure. The nature of the bond in Hb-Hp complex will be studied by characterizing the conditions for the formation and stability of the bone. Glycopeptide fragments of Hp retaining the ability to bind Hb will be separated and characterized. The method of affinity chromatography is to be used in both of these studies. Our current work on models of Hp polymers and of their interaction with Hb will be pursued. These experiments involve isolation of individual polymers and the determination of the polypeptide content by acrylamide gel electrophoresis, and the measurement of their molecular weights by ultracentrifugation. The relation of the Hb-binding function of Hp to the evolution of its structure will be an extension of current immunogenetic studies.